This invention relates to chain links and, more particularly to chain link conveyors formed of a plurality of chain links assembled by pivot means so that adjacent chain links can turn in a hinge like manner around the pivot means holding them together, with means being provided for positionably securing the pivot means.
Chain links of the aforementioned type are normally produced of plastic by injection moulding, with each link being moulded as a one-piece unit which, either with steel or plastic pivot rods, is assembled to form an endless chain link conveyor, drawn by one or more driving wheels.
Since chain links of the aforementioned kind are only a few centimeters in length, e.g. in the range of 5-15 cm, in the production of a conveyor, a large number of chain links are assembled by pivot rods or similar assembly elements.
In, for example, U.S. Pat. No. 4,080,842 is known a two-part pivot for use in the assembly of chain links for chain link conveyors is proposed, wherein each pivot part has a head at the one end and an inclined section with locking ridges at the other end. The pivot parts are assembled by forcing the locking ridges into engagement with each other, and the result is a substantially permanent assembly, in that the pivot is normally ruined upon separation. This principle can be used only with soft plastic pivots which can be deformed slightly during the assembly operation. Moreover, as the chain links are gradually worn and the pivot is given greater and greater clearance, the pivots are inclined to separate from each other at the joint.
It is also generally known to use plastic pivots which, after the assembly, are deformed by heating in the formation of a head. The pivot thus sits permanently in the chain and must be ruined for disassembly. This construction makes disassembly difficult and requires special tools for heating when assembling the pivots in the chain links.
With the use of steel pivots for the assembly of chain links for chain link conveyors, the normal pivot locking mechanisms may be utilized, e.g. an annular groove in each end of the pivot in which a locking element such as a circlip can be secured. However, such constructions considerably increase the cost of the chain link conveyor, with the reason being that the pivots are usually made of hard steel which is difficult and expensive to machine, and the assembly and disassembly require special tools.
The object of the present invention is to provide a chain link which is arranged in such a manner that the assembly and disassembly of pivots, regardless of which material the pivots are made, is to a wide extent simplified and made cheaper, in that completely smooth pivots can be used.
In accordance with advantageous features of the present invention, a chain link is provided wherein a groove is provided in each side of each chain link opposite at least one of the pivot bores of the chain link, with the groove being adapted to receive and securably hold a locking dowel arranged so as to restrict a displacement of the pivot in an axial direction.
In accordance with the present invention, the locking grooves and the chain links are formed at the same time that the chain link is injection molded, and the locking dowels for restricting the displacement can be similarly injection molded, for example, of the same plastic material as the chain link, or possibly of a slightly softer plastic material. Moreover, the pivots used in this construction are completely smooth and do not require any finishing work in the form of grooves, holes, or the like, thereby considerably reducing the cost thereof, which is particularly significant, in the case of steel pivots.
By virtue of the very simple construction of the locking dowels in accordance with the present invention, a simple assembly and disassembly is realized without the use of any special tools and, consequently, it is possible for the operation to be fully automated so that the assembly of chain links for a chain or chain track can be carried out in a fully automatic matter by a relatively inexpensive assembly machine.
Presently, both assembly and disassembly of chain link conveyors is carried out manually and it is a considerable advantage that the chain links can be disassembled, for example, when replacing worn or defective links in a chain, completely without the use of special tools thereby enabling the repair to be effective on sight.
In order to disassemble a chain link constructed in accordance with the present invention, all that is necessary is the removal of the locking dowels at one side of the link or links which are to be replaced and the pulling or pushing out of the pivots. The assembly of the chain is carried out merely by inserting the pivots, after which the locking dowels are inserted so that the pivots are once again positionwise secured.
This assembly and dismantling principle can be used on many types of chain link conveyors comprising identical chain links with pivots, but has been developed mainly for those which run in a straight-out manner and which have steel or plastic pivots.
In order to ensure that the locking dowel always sits in a sufficiently firm manner, even though the chain is exposed to great mechanical influences in the form of vibrations, jolting etc., e.g. from the goods which are loaded on the conveyor the groove is undercut, for example, into a dove-tail groove, which is not throughgoing from edge to edge, and the locking dowel has a cross-sectional profile corresponding to the groove profile. The groove includes means, such as, for example, a snap-edge means or collar means on a side facing the chain link, with such means being arranged to engage the pivot bore. With such an arrangement, the locking dowel can still be inserted and removed completely without the use of special tools.
Chain link conveyors of the type described above are often in the form of a number of parallel-running chains which make up broad conveyor tracks, often in such a manner that the pivots in the chain links extend throughout the whole of the breadth. For reasons of production tolerances, stretching of the chain under great loads etc., there is a possibility of transverse movement of the chain links, the result being that unacceptable longitudinal slots arise in the conveyor track.
Chain link tracks of the aforementioned type may be arranged to be coupled together with at least one adjacent change in the formation of a conveyor chain track with the adjacent chain link in each chain being assembled by pivot means which are throughgoing for an entire width of the chain track so that the chain links may be turned in a hinge-like manner around the pivot means which holds them together, with means being provided for positionwise securing of the pivot means. Chain link tracks of this type are generally selected to solve certain conveying tasks.
In a chain link track of the aforementioned type, at least the chain link sides which face towards an adjacent chain and opposite the pivot bores of the chain links, a groove is provided in which the locking dowel can be inserted before insertion of the pivot, with the locking dowel having a central bore for the pivot and being arranged for simultaneous engagement with the grooves in two chain links which abut each other on the same pivot thereby coupling these chain links together. By using such a locking dowel, the chain links lying adjacent to each other are locked together and thus any relative transverse displacement between the chain links is impossible. However, this arrangement has no effect on the simple assembly and disassembly afforded by the present invention in that the locking dowels have a throughgoing bore for the pivots so that, during assembly, the locking dowels are merely inserted prior to insertion of the pivot means and, for disassembly, the pivot means is removed first after which the locking dowels can easily be removed. A chain assembly with such locking dowels can also be fully automated.
When such together-locking dowels are mounted, they sit solidly secured by the pivot, and therefore under no circumstances can they be lost or loosened during operation.
The groove of the present invention is undercut in the form of, for example, a dove-tail groove which is not throughgoing from edge to edge, with the locking dowel having a cross-sectional profile corresponding to the cross-sectional profile of two abutting grooves thereby resulting in a construction which holds the chain links together, even in the event of very great forces in the transverse direction, e.g. forces which arise when the conveyor track is being sluiced under high pressure and the sluicing pressure is applied directly against the slot between the tracks.
In accordance with the present invention, an undercut groove is provided in each side and arranged so as to be assembled into chain tracks with through-going pivot means while using both locking dowels for positionally securing the pivot means and locking dowels for coupling together the chain links on the same pivot means, whereby the same chain link can be used in the formation of tracks of any desired breadth, and both locking dowels for positionwise securing of the pivots and locking dowels for the locking together of adjacently-lying chain parts can be used, also in the same chain conveyor.
Although the invention described above can be used in connection with many types of chain link, it has proved particularly advantageous for the chain link having a smooth or perforated support surface, from each side of which extend rows of traction or hinge eyes with through-going bores. The eyes on one side of the link are staggered in relationship to the eyes on the other side of the link and, the underside of the link comprises longitudinal, inclined ribs which are an integral part of the support surface and the eyes on both sides thereof. The ribs extend in pairs toward each other in the running direction and towards a rounded transverse rib piece which constitutes a point of engagement for a driving sprocket. Such chain links have low friction against the track on which they slide. The chain links can be produced with low weight and yet still with sufficient strength, the reason being that longitudinal traction forces in the chain are transferred from pivot to pivot by the ribs which extend from pivot to pivot, and the use of supporting cross-ribs between the hinge parts is avoided.
The ribs extending pair-wise towards the chainwheel's point of engagement automatically center the chain/the chains on the driving gears.
Advantageously, according to the present invention, the outer traction eyes in each side of each chain link are of a greater thickness than the remainder and each have an undercut groove which is configured in such a manner that it is not throughgoing to the upper side of the chain link but is throughgoing to the underside of the chain link and arranged for insertion of locking dowels from the underside whereby a top side of the conveyor from which the tracks for the locking dowels is not visible or accessible, and thus no places arise at which dirt can collect. Both the assembly and the disassembly is carried out from underneath by the insertion and removal of locking pivots.
The locking dowels in accordance with the present invention are adapted to be inserted in an undercut groove and a chain link for closing a pivot bore in the chain link, with the locking dowel being configured as a plate item with a rounded or tapered portion and two substantially straight side flanks which extend from the straight portion, all substantially with the same cross-sectional profile as that of the groove in which the dowel can be inserted. Means are provided for the positionalwise securing of the dowel opposite the pivot bore with a smaller diameter than the pivot journal is provided and disposed opposite the position of the journal of the pivot.
Moreover, a locking dowel may be provided for insertion into undercut grooves in chain links which, on a common pivot, abut against each other, with the locking dowel being configured as a one-piece unit by two side portions which are symmetrical about a plane at right angles to a throughgoing hole with at least the same diameter as the pivot, with each side portion having the same cross-sectional profile as a groove.
Moreover, in accordance with the present invention, the locking dowel between the side portions may be provided with a substantially cylindrical area which wholly or partly surrounds the bore.
By virtue of the above-noted features of the locking dowels constructed in accordance with the present invention, locking dowels are realized which are simple and easy to mount in that one can directly see on the dowels which end must be turned forwards for assembly. The locking dowels may also be configured rotationally symmetrical; however, by configuring the dowels in the manner described above, the track or groove is completely filled out and forms a smooth transition for the chain link so that dirt collecting corners can be avoided.
Moreover, by providing a substantially cylindrical area which wholly or partly surrounds the bore between the side portions, a well-defined slot results between.
The configuration of the chain links as characterized in claim 10 results in a well-defined slot between parallel-running chains, and thus it is ensured that the slot is so broad that it can be cleaned by sluicing, e.g. high-pressure sluicing. It is namely from the point of view of cleaning that it is undesirable that the chain links in parallel-running chains abut completely together, in that the crack which arises herewith can not be adequately cleaned.